Electrical precipitation apparatus



Sefit. 12, 1933. E ANDERSON 1,926,025

ELECTRICAL PRECIPITATION APPARATUS Filed Dec. 29, .1930 2 Sheets-Sheet 1INVENT OR. fl a/a flade/Ja/z M ATTONEYS.

Sept. 12, 1933. E. ANDERSON ELECTRICAL PRECIPITATION APPARATUS FiledDec. 29, 1930 2 Sheets-Sheet 2 I INVENTOR. [Va/a A delve/2 WM fi/Patented Sept. 12, 1933 UNITED STATES PATENT OFFICE Evald Anderson,

International San Marino, CaliL, assignor to Precipitation Company,

Angeies, Califi, a corporation of California Application December 29,1930 Serial No. 507,903

8 Claims.

This invention relates to apparatus for the electrical precipitation ofsuspended materials from gases and particularly to apparatus of the typein which a screen or pervious member is employed as a collectingelectrode and in which means are provided defining a material receivingspace or pocket at the opposite side of said collecting electrode fromthe region of the electric field, or'in other words at the opposite sidefrom the discharge electrode means. An advantage of this type ofapparatus is that a considerable portion at least of the suspendedparticles which are precipitated toward the collecting electrode'by theaction of the electric field pass through the openings of the screeninto said material receiving space or pocket where they are permitted tosettle in a region removed from the electric field and more or lessisolated from the main gas stream. It has been found, however, thatwhere the gas is permitted to travel for a considerable length past acollecting electrode of this type, there is a tendency for anappreciable portion of the gas stream to be diverted through theopenings of the screen and travel in the material receiving space orpocket rather than through the region of the electric field, thusremoving the suspended material carried by this portion of the gas witha multiplicity of openings distributed closely free passage of theprecipitated material through from the action of the electric field andalso interfering with the free gravitative settling of the materialwithin said space or pocket.

It will be understood that the term screen or pervious member" as usedherein includes not only a screen of woven wire, but any equivalentthereof, and in general, any member having an extended plane or curvedsurface and provided adjacent one another over its surface.

The principal object of this invention is to improve the efiiciency andeconomy of operation of a precipitator of this type, and particularly toprovide means acting to minimize orlargely pre' vent diversion of thegas stream into and along the material receiving space, so as to permitthe material entering said space to fall freely therein by gravity andto be collected. It is important that the means provided for thispurpose should be of such a nature as not to interfere with the theopenings of the collecting electrode screen or with the free settling ofsuch material to the collecting means which are provided at the bottomof such space.

According to this invention, the above objects are accomplished byproviding bafiie means extending within said material receiving space orpocket, extending transversely to the. direction of travel of the gas inthe electric field, and disposed at suitable intervals along the lengthof said space or pocket in the direction of gas flow. Said bafiiesinterpose such a relatively high resistance to passage of gas alongwithin the material receiving space or pocket that the flow of the maingas stream is confined substantially wholly largely to the region of theelectric field. The direction of gas fiow is vertical or substan-vtially so, and the baffles extend horizontally or substantially so, orat least in a direction transverse to the vertical, so that it isnecessary to provide openings permitting the precipitated material tofall through or between the baflies. Such openings, however, are ofrestricted size so as to minimize the passage of gas therethrough andare furthermore, for the same reason, preferably located at portions ofthe baflie members which are relatively removed from the collectingelectrode screens.

The invention may be applied to electrical precipitation apparatus ofvarious types of construction, for example, to apparatus 01' either theplate type or the pipe type.

The accompanyingdrawings illustrate the application of my invention toboth of these types of precipitators and referring thereto:

Fig. 1 is a partial vertical section of a plate type precipitatoradapted for vertical gas flow.

Fig. 2 is a partial section on line 2-2 in Fig. 1, with the collectingelectrode screen and the side wall of the material receiving meanspartly broken away.

Fig. 3 is a horizontal section of a pipe type precipitator embodying myinvention. I

Fig. 4 is a vertical section on line 4=4 in Fig. 3. l

Fig. 5 is a section online 5-5 in Fig. 4, partly broken away;

In the apparatus shown in Figs. 1 and 2 each collecting electrodecomprises two screens 31 ex--- tending in parallel vertical planes andspaced apart to provide a m terial receiving space or pocket 32therebetw The upper end of said space or pocket is closed by ahorizontally extending top plate or baflie 33, which vertically spacedhorizontally extending intermediate baflle members 34 are also providedat suitable intervals, said intermediate bafile members having openings35 therein for permitting downward passage of precipitated materialtherethrough. Such openings 35 are relatively restricted so as tominimize gas flow therethrough and are furthermore preferably located atthe central portions of the bafiles, midway between the two screens 31.Such openings are, therefore, relatively removed from the main gaspassages outside the collecting electrodes and this, together with thesmall size of such openings, reduces to a minimum the amount of gaspermitted to pass through the baflie members. Each of the baflle members34 may conveniently be formed by two angle bars 34a disposed as shown,so that the upper surface of each bafile member tapers downwardly andinwardly toward the opening 35 for facilitating passage of precipitatedmaterial into and through said opening. I may also provide verticalpartition members 36 extending midway between the screens 31 of eachcollecting electrode and dividing the space 32 into two parts, suchpartition members preferably terminating a short distance above andbelow the respective openings 35, as shown, so as to permit free passageof material through said openings. However, if desired, these partitionmembers may be entirely omitted.

A bafilemember 37 is also provided at the lower end of each collectingelectrode, which may be substantially the same as the intermediatebaflle members 34 above described, and which is similarly provided withan opening 38 permitting precipitated material to fall therethrough. Itwill be understood that in a vertical fiow precipitator the gas musteither enter or leave through the space below the level of the bottomends of the collecting electrodes, and in order to prevent the materialfalling from the collecting electrodes from coming into contact with thegas in this space I have shown the provision of material receiving ductsor passages 39 disposed beneath the respective collecting electrodes andproviding spaces 41 therebetween for inflow or outflow of the gas. Itwill be understood that said ducts or passages 39 may open at theirlower ends'into any suitable receptacle or hopper means for theprecipitated material.

The discharge electrodes 42 are shown as extending vertically in planesmidway between the respective collecting electrodes and supported attheir upper ends by means of bars 43 and provided with tensioningweights 44 at their lower ends.

Another form of apparatus adapted for vertical gas flow is illustratedin Figs. 3 to 5 inclusive, the collecting electrodes in this case beingof the pipe type. Each of said collecting electrodes comprises avertically extending screen 46 of cylindrical or other suitable shape,all of said screens being mounted within a suitable housing indicated at4'7 and connected at their upper ends to a top header plate 48. Thespace 49 around and between the collecting electrode screens and withinthe housing 47 constitutes a material receiving space or pocket, andsaid space may, if desired, be subdivided by means of two perpendicularsets of vertical partition plates 51 and 52 into rectangular spacesindividual to the respective collecting electrodes, although it will beunderstood that if desired one or both of these sets of partition platesmay be omitted.

Transverse bafile members 53 are providcd"at suitable intervalsintermediate the height of the collecting electrode screens, said bafilemembers extending in general transversely with respect to the directionof gas flow. Each of said baflle members is shown as comprising aninverted V- shaped channel having its length disposed horizontally, withthe apex or ridge 54 along the line of centers of a row of cylindricalscreens and with the upper surface thereof sloping downwardly andoutwardly toward openings 55 located substantially midway betweenadjacent rows of screens, for permitting downward passage of collectedmaterial. As before, said openings are of restricted area as compared tothe horizontal cross-sectional area of the space 49 and are located atparts of said space which are relatively removed from the tubularscreens 46. In order to minimize the tendency for clogging of saidopenings, the partition plates 51 which extend parallel to the length ofthe baflle members may be broken away for a short distance above andbelow the openings 55, and auxiliary baflle members 56 may be providedif desired, depending to a suitable distance below the lower edges ofthe bafiie members 53 for the purpose of minimizing the circulation ofgas between the cylindrical collecting electrode members. As in the formof the invention shown in Figs. 1 and 2, separate material receivingducts or passages 57 may be provided communicating with the openings 55between the lowermost bafile members 53, so as to carry off the materialfalling therethrough and prevent such material from reentering the gasin the header space 58 below the lower ends of the collectingelectrodes, such header space serving to conduct the gas to or from saidcollecting electrodes. The walls of the ducts or passages 57 also serveas closure means for the lower ends of the material receiving spaces 49so as to prevent entrance of gas thereto.

It will be understood that the discharge electrode means and thecollecting electrode means may be connected in the usual manner to anysuitable source of high voltage electric power, either unidirectional oralternating, but preferably unidirectional current obtained, forexample, by rectification of alternating current. The voltage sosupplied must be sufiicient to maintain effective electrical dischargefrom the discharge electrodes 42 or 61 respectively, and the electricalfield between said discharge electrodes and the collecting electrodes isof sufficient intensity to cause charged particles within said field tomove toward the collecting electrodes.

The discharge electrodes are shown as comprising wires or small rods 61extending axially within the respective tubular screens and through theentire length thereof, said discharge electrodes being supported attheir upper ends on supporting bars 62 mounted on suitable frame means63 and being provided at their lower ends with tensioning weights 64 forholding the same in centered position within the screens.

In the operation of either of the two forms of the invention described,the gas is passed vertically through the space between the discharge andcollecting electrodes, for example in an upward direction as indicatedby the arrows in Figs. 1, 2 and 4. The electric discharge from the hightension or discharge electrodes 42 or 61 respectively, in conjunctioiwith the electric field between said discharge electrodes and thecollecting electrode screens, serves to effect charging of suspendedmaterial contained in the gas and migration or precipitation of suchmaterial to ward and upon said screens, and it will be understood that aconsiderable portion of the material the surfaces of the screensfollowed by creeping of the precipitated material around to the innerside thereof. It will be understood, of course, that some of theprecipitated material may remain on the outer face of the screen untilit falls therefrom by gravity, butit has been found in' the operation ofprecipitators of this type that a very appreciable portion, and in somecases the major portion, of the precipitated material reaches theinterior of the electrode and falls withinthe material receiving spacetherein rather than outside the electrode. That portion of the materialwhich passes through the screens and into the spaces 32 or 49 fallsdownwardly within such spaces and through the openings 35 and 38 or 55and into the ducts or passages 39 or 57. The baflie members 34 or 53serve to minimize the flow of gas within the material receiving spacesof the collecting electrodes and confine the gas stream substantiallywholly to the region of the electric field between the discharge andcollecting electrodes, so as toeliminate the above mentioneddisadvantages which would result if the gas were permitted to bediverted out of the electric field and into these quiescent materialreceiving spaces. Due to the restricted area of the openings 35 and 55respectively, and also to the fact that said openings are disposed atpositions relatively removed from the collecting electrode screens, theupward flow of gas permitted through said openings is reduced to aminimum, and the transverse baiiles are therefore enabled to performtheir desired function of substantially preventing or vertical flow ofgas in the material receivingspaces behind the collecting electrodescreens.

The above mentioned advantages arising from the provision of transversebaflie means within the. material receiving pockets, intermediate theendsof the collecting electrode members with respect to the direction ofgas flow, may therefore be realized with either of the types ofapparatus above described, and it is evident that the principles of thisinvention may be applied to a wide variety of constructions, those abovedescribed being given merely by way of examples.

I have found by actual experiment that the provision of transversebailles intermediate the length of the material receiving space ofascreen electrode of the general type above described produces a verymarked increase in the precipitating eiliciency thereof, and that, ingeneral, increasing the'number and decreasing the spacing of suchbaflles, further increases the efliciency. The following set of tests,for example, were made with a cylindrical screen electrode and verticalgas flow, with the same suspended material (a potash fume) atapproximately the same concentration, and with substantially identicalelectri cal conditions, the only important distinction between theconditions maintained being with respect to the number of baflles used.In all of the tests the gas was passed upwardly, and the upper end ofthe material receiving space outside the screen was closed. In the firsttwo sets no other transverse baflle was provided. In the next two tests,a baflie was provided atthe lower end of the materialreceiving space,and in the last two tests .two baflies were provided, one at the lowerend-and one at the mid-height. The results obtained are shown in thefollowing table:

Concentration of! I)ume mg.per en. t. m m Test No. 23 3: (percentcollected) Inlet Outlet 0 41. 2 6. 81 83. 5 0 39.5 8.6 78.2 0 80.8 145.8 4.09 91.1 1 41.0 5.22 87.3 1, 8E2 2 41.9 2 72 93.6 -2' 55.3 2.80.94.9 Average .2 94.2

passage of collected material therethrough, said opening means in eachbaille member above the lowermost being positioned to deliver collectedmaterial from the portion of said space above that baflle member to theportion of said space 11:) below that baiile member in such manner thatall of the material collected in said space is delivered through theopening means in the lowermost of said baffle members, dischargeelectrode means spaced from said screen at the side oppositesaidmaterial receiving space, and means for passing gas substantiallyvertically between said discharge electrode means and said screen.

2. In an apparatus for electrical precipitation of. suspended materialfrom gases, a collecting electrode comprising a vertically extendingscreen, means defining a material-receiving space atone side of saidscreen and closing the upper end of said space, baflle means extendinghorizontally within said space and transversely thereof at a levelintermediate 'the upper and lower ends of said space and provided with arestricted opening permitting passage of collected material 7therethrough from above said baflle means into the portion of said spacebelow said bai'fle means, additional baflle means disposed adjacent thelower end of said screen and partially closing the lower end of saidmaterial-receiving space but provided with an ope i permitting downwardpassage of collected material therethrough, means 1 positioned toreceive material falling through "said last-mentioned opening, dischargeelectrode means spaced from said screen at the side opposite saidmaterial-receiving space, and means for;

passing gas substantially vertically between said 4 discharge electrodemeans and said screen- 3. In an electrical precipitation apparatus, acollecting electrode comprising two screens spaced from one another andextending in substantially parallel vertical planes and-providing amaterial receiving space therebetween, means substantially closing theupper end of said material receiving space, and horizontally extendingbaflle means disposed between said screens extending across said spaceintermediate the upper and lower ends thereof said baille means beingprovided with openings of relatively restricted area. as compared to thecross-sectional area of said space and positioned substantially midwaybetween said screens.

4. In an electrical precipitation apparatus, a collecting electrode asset forth in claim 3, and comprising in addition, a vertically disposedpartition plate extending substantially midway between said screens andparallel thereto, said partition plate being broken away adjacent theposition of said openings in said baflle means.

5. In an electrical precipitation apparatus, a collecting electrodecomprising two screens spaced from one another and extending insubstantially parallel vertical planes so as to provide amaterial-receiving space therebetween, means substantially closing theupper end of said material-receiving space, a plurality of verticallyspaced bafile members extending horizontally within the space betweensaid screens and transversely thereof and each provided with arestricted opening permittingdownward passage of collected materialtherethrough, said restricted opening in each of said baflle membersdisposed substantially midway between said screens.

6. In an electrical precipitation apparatus, a collecting electrodeconsisting of a vertically disposed tubular screen, means for passinggas longitudinally through the tubular space within said screen, adischarge electrode member extending centrally within said tubularscreen, means defining a material-receiving space outside said tubularscreen, and a plurality of vertically spaced baflle members extendingacross said material-receiving space and transversely with respect tothe length of said screen, each of said baflle members being providedwith restricted opening means for passage of collected materialtherethrough, by gravity, from above said bafile member to below saidbaiile member, in such manner that all of the material collected in saidreceiving space is permitted to fall successively through the openingmeans in the respective bafile members and is discharged through saidopening means in the lowermost baflle member.

7. In an electrical precipitation apparatus, a housing, a plurality oftubular screen collecting electrodes extending vertically within saidhousing, means for passing gas vertically through the interiors of saidcollecting electrodes, discharge electrode members extending centrallywithin the respective collecting electrodes, the interior of saidhousing outside said collecting electrodes constituting amaterial-receiving space, means substantially closing the upper end 01said material-receiving space, and baflie means extending within saidmaterial-receiving space, between adjacent collecting electrodes andtransversely with respect to the length of said electrodes, and providedwith restricted openings for downward passage of material therethrough.

8. In an electrical precipitation apparatus, a construction as set forthin claim 7, and comprising in addition, vertically disposed partitionmeans extending within said material-receiving space and betweenadjacent collecting electrodes.

EVALD ANDERSON.

